In some decision models, the input data must conform to an industry-standard xml schema in which elements of interest are many levels deep. Converting such a schema directly to a FEEL item definition requires very long path references. The xpath language has a descendants operator that significantly shortens the path expression. I propose a similar operator (or, less ideally, a function) for FEEL.

An example is MISMO from the Mortgage Bankers Association. In home appraisals, one item of interest is the Appraiser. To reference the Appraiser from the FEEL item definition generated from the xsd requires this:
MESSAGE.DOCUMENT_SETS.DOCUMENT_SET.DOCUMENTS.DOCUMENT.DEAL_SETS.DEAL_SET.DEALS.DEAL.SERVICES.SERVICE.VALUATION.VALUATION_RESPONSE.VALUATION_ANALYSES.VALUATION_ANALYSIS.PARTIES.PARTY[ROLES.ROLE.ROLE_DETAIL.PartyRoleType="Appraiser"][1]

In xpath, omitting namespace prefixes, the descendants operator // simplifies this considerably:
MESSAGE//PARTY[.//PartyRoleType='Appraiser']

If // were used as a FEEL descendants operator, you would need only
MESSAGE//PARTY//PartyRoleType="Appraiser"[1]

To get the Appraiser's name, instead of
MESSAGE.DOCUMENT_SETS.DOCUMENT_SET.DOCUMENTS.DOCUMENT.DEAL_SETS.DEAL_SET.DEALS.DEAL.SERVICES.SERVICE.VALUATION.VALUATION_RESPONSE.VALUATION_ANALYSES.VALUATION_ANALYSIS.PARTIES.PARTY[ROLES.ROLE.ROLE_DETAIL.PartyRoleType="Appraiser"].INDIVIDUAL.NAME[1]

you would need only

MESSAGE//PARTY//PartyRoleType="Appraiser"//NAME[1]

The names of the number() function in note 1 at the end of Table 72

The current mechanism for importing in DMN requires a name attribute to be a prefix to imported elements names.
Importing an item definition named Person becomes import. Person when referencing it from the local model.
This is confusing to some business users.

We would like to allow the import into the default namespace by specifying an empty name.
This, of course, has the potential of creating name collisions for the imported elements.
We suggest that when a name collision occurs for one of the imported elements, the local element is kept and the imported one is discarded.

For tools to clearly identify the version of a DMN file or FEEL expression, the XML namespaces of DMN, DMN DI, and FEEL should be updated.

Namespace URIs must be backwards compatible with the scheme applied in previous versions for tools that support multiple versions in parallel. See:

• https://issues.omg.org/browse/DMN12-62?focusedCommentId=18500&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-18500
• DMN13-191
• DMN14-166

DI and DC namespaces can stay the same as DMN 1.4 DI is still based on the same DI 1.1 specification and "OMG Policy for Versioning of Specification URIs, File URIs, and XML Namespaces in OMG Specifications", states explicitly:

Note: if a spec has many machine readable files, and only some of them change at a given specification version, then only the changed files should get new URIs. That could mean a mixture of URI date segment values for a given specification version..

The specification is not clear in section 6.3.3 if multiple imports into the default namespace are allowed and how the import precedence is managed.

With reference to DMN v1.4 dtc-21-12-01 pdf
Table 66 list all the properties for duration FEEL value type, the property hours (plural) is inadvertently spelled with the capital H, but it should be lower case hours

Section "4.1 Acknowledgements" is missing paragraphs to acknowledge the DMN 1.4 and 1.5 contributors, especially since some people left the task force.

The copyright section needs to be updated.

Currently concatenating strings is not intuitive to users, as I always have to convert non string values to strings using the built-in `string` function.

So

```
"Today is " + now() = null
```

In order to yield the actual string you explicitly convert `now()` to its string representation:

```
"Today is " + string(now()) = "Today is 2021-12-12"
```

A more user friendly behavior would be to coherse the second argument to string if the first argument is already a string. This always yields a string representation of the thing. If it is not what I desire I can use custom stringification mechanisms explicitly.

We'd need to amend the Table 57 (page 128, https://www.omg.org/spec/DMN/1.4/Beta1/PDF) to support such cohersion.

—

Additional details on this case can be found in https://github.com/dmn-tck/tck/issues/538 (DMN TCK issue on this topic).

There are 2 typos in the examples

duraion("P0DT25H") and duraion("P0Y13M"))

Should be

duration("P0DT25H") and duraton("P0Y13M"))

In this couple of chapters, "duration" is written "duraion" (without "t" - 2 occurrences)

Currently if a DMN model makes use of an external library of functions, the receiving tool may be challenged in also importing this library and execute on these new functions.

We should explore a way to make the interchanged model not only exchangeable but also executable.

There are many different Functions that are needed to make FEEL expressive enough for tackle the logic of various contexts/industries:
e.g Financial Functions, Healthcare Functions, etc. even advanced Mathematical functions or Matrix manipulation functions.

Currently these functions need to be imported in, and then all functions need to be prefixed with a namespace.
This not ideal as the business friendly name with space such as "annual interest rate" now becomes cryptic as "financial.annual interest rate"
or "discount as percentage" becomes "financial.discount as percentage"

DMN ItemDefinitions metamodel (section 7.3.3) specifies that and ItemDefinition can restrict its typeRef by using an allowedValues attribute that is defined as a UnaryTests:

An ItemDefinition element may restrict the values that are allowed from typeRef, using the allowedValues attribute. The allowedValues are an instance of unaryTests that specifies the allowed values or ranges of allowed values within the domain of the typeRef. The type of the allowed values SHALL be consistent with the containing ItemDefinition element. If an ItemDefinition element contains one or more allowedValues, the allowedValues specifies the complete range of values that this ItemDefinition represents. If an ItemDefinition element does not contain allowedValues, its range of allowed values is the full range of the referenced typeRef. In cases where the values that an ItemDefinition element represents are collections of values in the allowed range, the multiplicity can be projected into the attribute isCollection. The default value for this attribute is false.

This paragraph has a few contradictions with the spec:

• The last phrase is not clear about which attribute defaults to false, this whole paragraph talks about allowedValues and the intention must be that it refers to isCollection but that certainly confused us.
• The attribute allowedValues is a UnaryTests but its usage is not consistent with its usage in decision tables inputEntry. A UnaryTests is defined as an expression that evaluates to a boolean with an implicit argument to be tested (from its definition in section 7.3.2). However, this is not the way it is used here. Here it defines a range/enumeration of allowedValues and not an expression that is evaluated with an implicit argument.
  Our proposal would be to align the usage of UnaryTests with decision table inputs.
  This would allow extended use cases such as:

•  A validation of an email address domain: allowedValues => ends with(?, “@trisotech.com”) 

•  Validation that depends on sibling variables values: allowedValues => if OrderType = “Type A” then [“a”,”b”,”c”] else [“c”, “d”, “e”] 

•  Or something even simpler like not null: allowedValues => ? != null 

•  Length check on strings: allowedValues => string length(?) > 10 

There are currently FEEL functions to manipulate lists content: append, sublist, concatenate, insert before, remove, union, distinct values and flatten but it does not define a function to replace item(s) from a list.

Our proposal is to introduce a new list replace function.

The current para (below) does not provide an example with null which could lead to misinterpretations.

For convenience, a selection using the "." operator with a list of contexts on its left hand side returns a list of
selections, i.e. FEEL(e.f, c) = [ FEEL(f, c'), FEEL(f, c"), ... ] where FEEL(e) = [ e', e", ... ] and c' is c augmented with
the context entries of e', c" is c augmented with the context entries of e", etc. For example,

[ {x:1, y:2}, {x:2, y:3} ].y = [2,3]

FEEL for iteration statement context limits the iteration context (Section of 10.3.2.14 ) to integers:
"An iteration context may either be an expression that returns a list of elements, or two expressions that return integers connected by “..”. "

It would be useful to augment the iteration context to also allow dates.

This will allow to create simple decision logic that validates conditions for each date in the range and allows one to write decision logic that can validate the state on each day to calculate the number of days that meet a requirement.

An general example use case could be, how many days in the range [2021-01-01..2022-01-01] meets a certain complex logic.

A specific example of that would be to determine if the person and its spouse were both employed and living at the same address for at least the 3 of the last 5 years given a list of Job description for both (Date From, Date To, Employer) and a list of their declared residence for both (Date From, Date To, Address).

This can of course be calculated in a different way, but the logic of iterating on a date range and checking if the condition is true for every day and summing the number of days for which its true makes the logic a lot simpler to follow for a business user.

After adding support for scientific notation (https://issues.omg.org/browse/DMN15-107), there are incorrect parts in section 10.3.2.3.1:

1. Literals consist of base 10 digits and an optional decimal point.
2. FEEL does not support a literal scientific notation. E.g., 1 .2e3 is not valid FEEL syntax. Use 1.2*10**3 instead.

DMN ItemDefinitions metamodel (section 7.3.3) specifies that the allowedValues of a collection attribute are projected to its elements which prevents us from constraining collections.

For example:

• The collection size needs to be between 1-5 elements
• The collection can’t contain duplicates

Our proposal is to add an additional attribute to ItemDefinition named collectionAllowedValues to capture these constraints.

This statement was brought to my attention via DMN TCK email:

"If a decision element requires more than one business knowledge element, its value expression must be a literal expression that specifies how the business knowledge model elements are invoked and how their results are combined into the decision's outcome. "

This statement is either false or ignored by most vendors

This statement was brought to my attention via DMN TCK email:

"If a decision does not require any business knowledge models, its value expression must be a literal expression or decision table that specifies the entire decision logic for deriving the output from the inputs."

This statement is either false or ignored by most vendors

Currently the positive unary tests support all relational operators but not the equality operators (= !=). We should support them for consistency. For example, all the above operators are supported in comparison expressions (rule 49).

Business analysts have reported that they would like to have a consistent and more readable way to write rules and test cases with many comparison operators.

Currently the syntax of numeric literals does not support usage of exponents. This is quite useful when dealing with large numbers.

In the following bullet point:

In rule 62, the only permitted functions are the builtins date, time, date and time, and duration.

the correct reference is rule 60 where the date time literals are defined.